Slotted shear plate for electric shavers



1966 E. BAKKER ETAL I 3,292,251

SLOTTED SHEAR PLATE FOR ELECTRIC SHAVERS Filed July 8, 1964 INVENTORJ I EPPE aAKK EILDERT KINGMA United States Patent 3,292,251 SLOTTED SHEAR PLATE FOR ELECTRIC SHAVERS Eppe Bakker and Eildert Kingma, Drachten, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed July 8, 1964, Ser. No. 381,004 Claims priority, applicatggg lglsestherlands, July 26, 1963, 9 2 Claims. (Cl. 30-34651) The invention relates to a slotted shear plate for use with a shaving head of a dry shaving apparatus in which the slots have a greater width at the inlet ends. This device is of particular use with a shaving head having a rotating rim of cutters.

In known shear plates of this type the widened inlet or entrance of a slot serves to improve the entrapment of beard hairs and to guide them to the surface of the slot covered by the moving cutter. Therefore, the widened entrance formed a deep cut at the inlet and gradually tapered into the area covered by the cutter.

With an annular shear plate, along which a rim of cutters is adapted to rotate, the entrance of each slot is formed by a saw cut in the upper rim of the plate side, while the walls on either side of the entrance are often bevelled or rounded off to facilitate the entrapment of hairs. The hairs captured by the entrance are guided in the slot or guide groove, where they are cut off.

These known structures with a widened entrance involve the disadvantage that the skin penetrates in the entrance and is urged into the guide groove in which it bulges to an excessive extent so that-when the widened slot tapers gradually into the area covered by the cutter the bulging skin is held in the slot and is grazed by the cutter.

After the discovery-of the cause of grazing, which is particularly manifest in the case of a thin and soft skin, it has been found that this disadvantage can be overcome by arranging the widened parts completely outside the area covered by the cutter but within the rim of the shear plate.

The distance available for the widened parts between the entrance of the hairs in the slot and the area covered by the cutter is then so small that the widened part can no longer be narrowed gradually, so that skin portions which are excessively bulged are temporarily pushed off upwardly while it has been found that the width of the slot can be equalized to the value in the area covered by the cutter over a small distance which corresponds to a very small thickness of the slots without adversely affecting the shaving effect on the hairs entrapped in the entrance.

This relates in particular to a further ascertainment that long slanting hairs are bent over by the walls on either side of the entrance and urged beneath the slots, so that these hairs cannot penetrate into the guide groove and will not be cut off. Consequently, shaving takes unnecessarily more time, since these hairs are captured satisfactorily and cut off only during a second or third shaving movement.

In an advantageous embodiment of the present invention, the foregoing is improved by closing the widened part of the slot at the outer end thereof by means of a rim of the shear plate extending in a direction normal to the cutting face at least substantially to the level of the edges of the cutting face covered by the moving cutter.

Thus, the hairs are compelled to glide in a curved position across said edge, so that after having sprung up in the widened parts the hairs can freely enter the guide groove. Moreover, an effective protection of the skin from excessive penetration is obtained by the support of the skin from the outer edge of the widened part, so that a wrinkle of the skin cannot enter at the side of the plate a widened 3,292,251 Patented Dec. 20, 1966 ice I entrance and be slightly compressed upon further penetration, excessive bulging being thus avoided. It is no longer necessary to form an entrance with sharply bevelled walls, since the hairs are captured by the widened parts.

Blocking of an entrance formed by an incision in the side Wall of the plate due to skin and fat particles, does no longer occur as in the past constructions, since the widened slot is completely open on the lower side.

A further advantage of the present invention is that the side wall may now be thinner than in the case of an annular shear plate of known structure, in which the thickness was utilized for providing an entrance of ample size having a Width tapering to the rear.

An advantageous embodiment in which the laminations extend in a substantially flat, uninterrupted plane, the face concerned being bent over at one end substantially at right angles on either side of the slots, is characterized in that the slots terminate directly inside the bentover edge in a bore.

Although the widened part of the slot may be shaped in any form, it has been found that a circular widened part has the most favorable properties for supporting the skin, so that excessive bulging is avoided and the trapped hairs are guided in the slot. This provides a further advantage in that the apertures may be made in a very simple manner and that a sturdy structure is obtained, so that the thickness of the slots in the area, covered by the cutter may be small, which is desirable for cutting the hairs closely.

It is advantageous to construct the plate so that the widened part of the slot is provided in an area of the shear plate where the thickness of the material with respect to that of the slot in the area covered by the cutter is enlarged, preferably so that this thickness gradually increases towards the end having the slot.

Thus, at the ends the slots of the shear plate are satisfactorily supported, so that each slot is as thin as possible for a satisfactory shaving operation at the area where it is in contact with the driven cutter. Moreover, the bores may be provided in a wall portion of suitable thickness, while the height of the walls where the hairs must enter the cutting area of the slot is small.

The invention will now be described more fully with reference to the drawing, which shows diagrammatically a few embodiments thereof.

The above and other features, objects and advantages of the present invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings.

FIG. 1 is a plan view of a sector of shear plate of annular structure for cooperation with a rotating rim of cutters.

FIG. 2 is a cross sectional view taken on the line II-II in FIG. 1.

FIG. 3 is a plan view similar to FIG. 1 of a second embodiment of the invention.

FIG. 4 is a sectional view taken on the line IV- IV in FIG. 3 and FIG. 5 is a plan view of a third embodiment of the invention.

The shear plate according to the invention is formed in known manner like a lid, the central portion 1 of which is slightly sunk with respect to the annular outer portion, which constitutes the shear plate proper. The shear plate is provided with slots 3, 4 and 5, the directions of which are tangential to a circle around the center of the shear plate. The trajectory 7 of the shaving slot, the boundaries of which are indicated by broken lines, is that covered by the driven cutter. The driven cutter (not shown) travels along the lower side of the shear plate 2 and cuts the hairs projecting through the slots 3, 4, 5, the width of the slot being such that in the most favorable case the hairs are cut off closely along the skin. The slots 3, 4, 5, however, extend beyond the trajectory 7 and terminate near the outer edge of the shear plate in a circularly widened aperture 8. The edge 11 is prolonged ap proximately up to the cutting face engaging the lower side of the slots in the zone. Towards the central portion 1 the slots 3, 4 extend up to the end of the shear plate 2, where they form grooves 10 in the cylindrical intermediate wall 9. With the shear plates hitherto known, the outer Wall 11 had the same thickness and the slots formed therein deep grooves, termed entrances. However, the invention oflers the possibility of making a thin side wall 11 with only the wall of the shear plate 2 being slightly thicker at said place than at the area of the trajectory 7 in order to stiffen the shear plate. When the skin glides over an aperture 8 any comparatively long hairs at said place can spring up readily and be guided into the slots 3, 4. This is permitted by the small thickness of the slot at the area of the aperture 8. A circular aperture is found to be most favorable for preventing excessive bulging of the skinwhile the skin penetrates to a desired extent in the slot, since the skin is supported substantially throughout the circumference. It is found that this support sufiices for preventing excessive bulging, even when the slot is prolonged beyond the circular aperture, which is indicated at the slot 4 (FIG. 3) and where the slot 4 has a widened part 12 near its aperture on the inner edge of the shear plate 2, the slot being prolonged beyond said aperture up to the edge.

From FIG. 4 it will be apparent that also the wall 9 is thin and that the shear plate 2 is slightly thicker at this area than in the trajectory 7. The groove 10 is shorter than that of FIGS. 1 and 2. The prolongation of the slot 4 to a groove 10 is important for maintaining the advantages of a ready entrance for the hairs without involving the disadvantages such as an excessive bulging of the skin.

The apertures 8, 12 may be obtained by boring, but from a manufacturing point of view it is often advantageous to provide the widened parts by incisions of the shear plate, so that a widened part 13 (FIG. is obtained, While the wall portion 11 is arranged afterwards.

This form is found to be extremely advantageous and fically illustrated or described and that in the illustrated i embodiment certain changes in the details of construction plate, each of said slots being widened into generally circular apertures at the end of the top surface of said shear plate adjacent to the outer periphery thereof, said apertures being located in said top surface of said shear plate beyond the rotational path of said cutters but within said outer side wall of said shear plate and spaced therefrom.

2. A shear plate for use with a rotating rim of cutters in a shaving head of a dry shaver as claimed in claim 1 wherein the cross-sectional thickness of the material of the top surface of said shear plate at the area of each of said apertures gradually increases toward said outer side wall.

References Cited by the Examiner UNITED STATES PATENTS 2,181,038 11/1939 Wirnberger 30-34.2 X 2,205,905 6/1940 Muros 30-43 2,206,551 7/1940 Muros 3043.92 2,223,156 11/1940 Benner 30-4392 2,251,577 8/1941 Rand 30354 X 2,309,431 1/1943 Alexay 30-342 X 2,331,274 10/ 1943 Martin 3043.92 2,336,638 12/1943 Rand 30354 X 2,494,463 1/1950 Vivie 30-34 2,494,464 1/ 1950 Vivie et a1. 30354 X 2,578,974 12/1951 Hinds 3043.92 2,616,170 11/1952 Keblusek 30--354 X FOREIGN PATENTS 980,755 1/ 1951 France. 469,782 8/ 1937 Great Britain.

WILLIAM FELDMAN, Primary Examiner.

MYRON C. KRUSE, Examiner. 

1. A SHEAR PLATE FOR USE WITH A ROTATING RIM OF CUTTERS IN A SHAVING HEAD OF A DRY SHAVER HAVING A TOP SURFACE EXTENDING IN A SUBSTANTIALLY FLAT PLANE AND PROVIDED WITH A PLURALITY OF SPACED SLOTS THEREIN, SAID SHEAR PLATE HAVING AN OUTER SUBSTANTIALLY FLAT SIDE WALL EXTENDING SUBSTANTIALLY PERPENDICULAR TO THE PLANE OF THE TOP SURFACE OF SAID SHEAR PLATE, EACH OF SAID SLOTS BEING WIDENED INTO GENERALLY CIRCULAR APERTURES AT THE END OF THE TOP SURFACE OF SAID SHEAR PLATE ADJACENT TO THE OUTER PERIPHERY THEREOF, SAID APERTURES BEING LOCATED IN SAID TOP SURFACE OF SAID SHEAR PLATE BEYOND THE ROTATIONAL PATH OF SAID CUTTERS BUT WITHIN SAID OUTER SIDE WALL OF SAID SHEAR PLATE AND SPACED THEREFROM. 